This invention relates generally to resurfacing machines and more particularly to devices of this type which are adapted to impart a desired, predetermined contour to portions of a workpiece, such as a turbine vane or the like.
After extended periods of use, the vanes employed in turbine engines tend to become worn along their air foil surfaces due to heat and abrasion from particles of sand or debris which are encountered during operation. In addition, small surface cracks tend to develop. When these occur, it is necessary to replace or repair the vane since such cracks will in time deepen and ultimately cause failures. Because the fabrication of these units is expensive, involving close tolerances and special metal alloys, it has been found desirable to refinish worn or damaged vanes whenever possible, instead of merely discarding them and substituting new units. Generally the vane surface is built up at the worn area, as by a plasma spray process described in one of the co-pending applications above identified. Following such buildup, small amounts of metal are removed by grinding, resulting in a restoration in the original vane dimensions, to thereby enable them to again be placed in use. One of the problems encountered in removing controlled amounts of material is that it has been difficult to judge how much metal has to be removed after the process has begun. In addition, achieving good uniformity from one unit to another is not had when the grinding or resurfacing is done by hand. In the latter case, it is likely that too little material will be removed on certain portions of the vane, with too much being ground off at other areas. Accordingly, it has been found that resurfacing such air foil surfaces is exceedingly difficult to accomplish by hand, in view of the close tolerences involved.
Specialized machines have been developed for resurfacing limited areas of the vanes, such as the leading edge, or the convex air-foil surface thereof. However, such devices were operable only over a portion of the vane surface. Repair or refinishing of other portions frequently required separate operations in multiple machines.